OBJECTIVE: 1. The formulation and continued revision of a theory of the basic processes of retardate discrimination learning, including attention, retention, learning, unlearning, generalization, perception and transfer. 2. Collection of experimental data providing empirical tests of the theory. 3. Development and application of methods for the measurement of the growth and decline of retardate intelligence. 4. Comparisons of retardate behavior processes with those of other subjects. 5. Application of basic knowledge to solution of problems of retardate education including the development of efficient experimental methods and training techniques especially suitable for retardates.